SENSATION-COGNITION COMPUTER EMPLOYING {37 t{38 {11 TEST CALCULATIONS

ABSTRACT

A patient who may be unable to cooperate is tested for auditory, visual and somatosensory perception. The apparatus includes an electroencephalograph, programmed stimulators, a t test computer including an average response computer and a recorder. Evoked responses of the patient are elicited and the patient&#39;&#39;s shortterm memory is tested.

United States Patent John 7 Dec. 25, 1973 [5 SENSATION-COGNITION COMPUTER 3,498,287 3/1970 EMPLOYING T TEST CALCULATIONS 39879487 4/1963 3,574,450 4 1971 [75] Inventor: Erwin Roy John, Riverdale, N.Y. 1090 5344 5/1953 2,860,627 11/1958 [73] Assgnee' g j' clffsde Park 3,339,063 8/1967 Norsworthy 23s 150.s3

[22] Filed: 1971 Primary ExaminerWilliam E. Kamm [21] Appl. No.: 173,604 Attorney-Eli0t S. Gerber Related US. Application Data [63] Continuation-impart of Ser. No. 877,948, Nov. 19,

I969, abandoned. [57] ABSTRACT A patient who may be unable to cooperate is tested (g1 "128/1611: for auditory, visual and somatosensory perception 58 d 2 1 The apparatus includes an electroencephalograph, 1 I o are 5 g 5 3 l 1 l programmed stimulators, a t test computer including an average response computer and a recorder. Evoked responses of the patient are elicited and the patients [56] References and short-term memory is tested.

UNITED STATES PATENTS 3,172,404 3/1965 Copenhauer et a1 l28/2.l B 5 Claims, 16 Drawing Figures Tl mER PRoGRHm SELECTOR 1- lfd SWlTCH PATENTEB I975 3.780.724

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INVENTOR.

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E. ROY JOHN O. v Q4 -t ATTORNEY PAIEmEunznzsms SHEET [1F 4 m GI N mam INVENTOR f. ROY Jomv ZZAXM TIL wAWW Hum. N\\

A TTORNE Y SENSA'TION-COGNITION COMPUTER EMPLOYING T" TEST CALCULATIONS This is a continuation-inpart of Application Ser. No. 877,948, filed Nov. 19, 1969 and now abandoned, and entitled Sensation-Cognition Computer."

DESCRIPTION The present invention relates to patient testing and more particularly to the testing of neural responses to auditory, visual or sensory stimuli, and to the perception of orderly relationships between stimuli.

Generally, the testing of auditory, visual or somatosensory systems requires the voluntary response of the patient. For example, eyes are examined by showing a chart having characters or pictures. The person being tested tells what he sees. Similarly, hearing is tested by presentingvarying intensities and frequencies of sound. The person being tested tells when he can, and cannot, hear the sounds.

But, if the person being tested cannot or will not cooperate, the testing becomes difficult. For example, the person being tested may be an infant or a person unable to speak due to injury or other causes. Some subjects cannot, or will not, say if they can hear a noise, see a chart or light, or feel a sensory stimulation.

The present invention provides a method for testing whether hearing, vision or tactile sensation is impaired, and to determine the likelihood of mental retardation. The prior art points out the existence of a widespread interest in the testing of children, more specifically the testing of infants. In a study by Beasley (Beasley, WC. 1933, Child Development, 4, 106-120, 55-56) an infants ability to fix his gaze on a light (stimulus), and to follow it with his eyes as it moved, was investigated. Beasley found that infants varied considerably in their ability or willingness to fix their gaze on an object and further, after birth, some infants display uncoordinated eye movement.

Another study in this area is that of Marquis-(Marquis DR 1931, Can Conditioned Responses Be Established in the New Born Infant? Journ. of Genetic Psychology, 39, 479-492, 74-75). Marquis was concerned with the subject of learning in early infancy, in particular with the question of whether during the first days of life an infant could acquire a conditioned response. Infants were bottle-fed from birth. At each feeding a buzzer was sounded. Marquis found that at 3 to 6 days the infant test subjects exhibited many responses related to feeding in response to the buzzer alone. It should be noted, however, that, since an infants response to a stimulus may be generalized, some of the observed effects might have occurred even if feeding had not been used as the conditioning stimulus.

In a later study, Marquis (l94l-Journ. of Experimental Psychology, 29, 263-282, 68, 75-78) directed his attention to the question of whether infants learn a feeding schedule within the first 10 days of life. The body activity of the infant subject was measured with the aid of a device supporting his bassinet. The results of the study show that infants on three-hour feeding schedules learned to expect food at the end of three hours.

Another interesting study in this area is that of Kantrow (Kantrow, R.W. I937 Studies in Child Welfare, 13, No. 3, Univ. of Iowa Press 74-75). Kantrow, working with infants ranging in age from approximately 1% to 4 months, found that they learned to respond to buzzing as a signal for food and, further, that they also learned to discard false signals, that is, buzzing that no longer meant food.

The method employed by Kantrow suffers, however, from the disadvantages common to all of the methods employed in the aforementioned prior art studies. The immature infant subject can do little, or nothing, to cooperate with the tester. The tester is therefore forced to cooperate with his subject. Further, the tester is forced to gauge the infant subjects response overtly, by what the infant does when exposed to the stimulus. Reliance upon the testers observation of the infants overt acts introduces the possibility of human error.

The instant invention attempts to resolve the abovementioned disadvantages inherent in the prior art testing methods. In the method of the invention herein disclosed, the tester does not have to rely on the test subjects overt responses to a stimulus. Thus, the element of human error inherent in the prior art methods is substantially reduced, if not totally eliminated.

The method of the invention contemplates presenting the test subject with a series of stimuli controlled by a programmed timer. The electrical responses of the brain to these stimuli are detected by electrodes attached to the appropriate regions of the head and amplified by an electro-encephalograph (EEG). The evoked responses to these stimuli are then extracted from the ongoing EEG activity by an average response computer (ARC). The significance of the extracted signal is automatically tested, on a statistical basis, by a t test computer. The signal, if deemed significant by that test, is then recorded.

The functional assessment of a particular sensory system is accomplished by presenting a series of stimuli in that sensory modality, computing the average evoked response, and determining its statistical significance. The presence, or absence, of the evoked response provides an indication of whether the sensory stimulus caused neural impulses from the peripheral sensory receptor (eye, ear, skin, etc.) to propagate through the central nervous system to the cortex. In addition, the detailed waveshape of the evoked and averaged response may be presented to permit evaluation of whether the response process includes all of the electrophysiological features usually considered normal." For example, a group of waveshapes may indicate sensory malfunction.

The instrument provides a functional assessment of the ability of an individual to perceive orderly relationships between stimulus patterns, which may be a way to evaluate fundamental cognitive processes and shortterm memory. Five specific methods for cognitive assessment are presented. The stimulus, to carry out each method, is presented in a predetermined timed se quence, with the sequences being programs stored in the programmed timer and controlling the other circuits of the instrument.

The advantages of the method of the invention described herein are readily apparent. The early diagnosis of defective vision, defective hearing, or mental damage affords one the opportunity for instituting early corrective measures, training or special care.

Other objectives of the present invention will be apparent from the following detailed description, describing the inventors best mode of practicing the invention, taken in conjunction with the accompanying drawings. In the drawings;

FIGS. 1, 6 and 8 are block schematic diagrams of two embodiments of the testing instrument utilized in the methods of the present invention;

FIGS. 2, 3 3A-3C, 4 and are graphs illustrating a normal brain wave response to a predicted stimulus and illustrating a normal brain wave response to an unpredicted stimulus;

Flg. 7 is a chart showing a type of visual stimulus;

FIG. 9 is a block circuit diagram of the t test computer; and

FIGS. A, 10B, 11A, 11B, 12 13 and 14 are circuit diagrams of specific circuits used in the t test computer of FIG. 9.

THE TESTING SYSTEMS As shown in FIG. 1, the devices used are an electroencephalograph and programmed stimulators, switches, and an average response computer. Two contacts 1 and 2 are adapted for connection to the scalp of theper'son .being tested. The leads 3 and 4 to the respective contacts 1 and 2 are connected to amplifiers 5 and 6, respectively. The amplifiers may be preamplifiers to the electroencephalograph 7. The electroencephalograph 7 isconnected to a switch 14C which is connected to an average response computer 10 which, in turn, is connected to a pen recorder 11 or other indicating means. A suitable average response computer is described in Clynes U.S. Pat. No. 3,087,487. A simple stimulus is presented by the flashing light 13 or the click sounding device 14. Other stimulating devices are other sound producing devices and a device which produces a small shock or tap on the skin. The stimulating devices are controlled as to their sequence and timing by a program timer l2. Inputs to computer are switched at the proper time by switch 14 operated by timer 12. The timer 12 is controlled by a program. Preferably there are a plurality of alternative programs (five of which are described below) one of which is selected at a time by the program selector switch 15.

In the embodiment of FIG. 8 the devices used are an electroencephalography programmed stimulators, switches, a recorder and a t test computer, part of which is-an average response computer. Two contacts 1a and 2a, adapted for connection to the scalp of the person being tested, have leads 3a and 4a connected to preamplifiers 5a and 6a respectively. The preamplifiers 5a and 6a are connected to the electroencephalograph 7a which is connected to a switch 14b which in turn is connected to a t test computer. The t test computer 16a is connected to a pen recorder 11a or other indicating means. The stimulators 13a and 14a are controlled as to their sequence and timing by program timer 12a and the inputs to computer 16a are switched at the proper time by switch 14b operated by timer 12a. As in the other embodiments, the timer 12a is controlled by a program. Preferably there are available in the timer 12: a plurality of alternative programs (five of which are described below) one of which is selected at a time by the program selector switch a. For example, the program may be in the form of punched holes on a paper or plastic tape, or may be electronic. The program performs the following functions: (1) it controls each of the stimulators 13a and 14a so that they operate in the selected sequence and time, (2) it controls the average response computer so that it records on the selected channel at the selected time period.

THE T TEST COMPUTER The T test is a statistical test for a measure of the significance of the difference between two sample populations. For example, for a sample size of N 10, corresponding to 10 sweeps (ten repetitions of each stimulation), to obtain a level of significance P of 0.001

(the result occurring by random chance 1 in 1000) the t result must be 4.587. With 25 sweeps and P 0.001 the t result is 3.725.

Preferably both the number of sweeps N and the level of significance may be varied by dials on the t test computer 16a to set a predetermined t test standard. For example, the tester may set the maximum number of sweeps N at 25 and the level of significance P at 0.001. For each stimulus group either the t test of the evoked response (X values) compared to brain wave ongoing activity background (Y values), will exceed 3.725 (the predetermined 1 standard) or be less than 3 .725. If the t test evoked response result is larger than the standard, then there is only 1 in 1000 chance that the result was by accident and consequently the test shows that the subject very likely responded to the stimulus. Upon such I test result, the recorder 11a will record the presence of a response.

Preferably the t test computer.will send out its result to recorder 11a as soon as the predetermined t test standard is reached, even though the standard is reached before the maximum set number of sweeps. For example, ifN is set at 25 and the P set at 3.725 and the P value is exceeded on the 11th sweep, a control signal on line 15 will be sent and the remaining 14 sweeps omitted, since a satisfactory set of evoked responses has been obtained. Alternatively, at less cost, the t test computer 16a may be set at the factory to perform a fixed number of sweeps P to obtain a fixed value of t, thereby setting the level of significance. In this alternative, at each stimulation a "go-no go signal would be shown, for example, by the pen recorder or by a light.

The preferred embodiment of the 1 test computer is shown in FIG. 9. As shown, the computer has two inputs an X input on line 100 and a" Y input on line 101. The inputs 100 and 101 are to a two-channel sample and hold circuit 102. The purpose of the sample and hold circuit 102 is to sample the two signals X and Y and to hold them so that they become in phase. A suitable sample and hold circuit is shown in FIG. 10A. The output lines 103 and 104 of the sample and hold circuit 102 are each directly connected to one channel of a four-channel average response computer 105. In addition, the outputs 103 and 104 are connected to respective squaring circuits 106 and 107, the details of the squaring circuit being given in connection with FIG. 12. The average response computer gives a value of samples taken periodically in time divided by the number of samples, thereby providing a running average, that is, an average which changes with the additional samples. A suitable average response computer is described in Clynes U.S. Pat. No. 3,087,487. The number of samples N is determined by the sampling rate which is set by the clock pulses produced by an in ternal clock, such as a crystal controlled oscillator whose output is divided, within the average response computer 105. The output of the first channel 108 is the average of the sum of the values of X, i.e., the sum of the voltages of each of the samples-divided by the number of the samples N, which is the mean and may be expressed by the formula: (EX/N,)=M The output of the channel 109 of the average response computer 105 is the sum of the X values squared over the number of samples and may be expressed by the formula: (2X /N The output of channel 110 is the sum of the Y values over the number of samples and may be expressed by the formula: (ZY/N )=M and the output of channel 110' the sum of the Y values squared over the number of samples and may be expressed by the formula: (2 WIN Each of the channels is connected to a four-channel sample and hold circuit 111. The only purpose of the sample and hold circuit 111 is to permit the use ofa single digitizer with the average response computer 105 and to sample the results. An alternative is to have a digitizer for each of the channels, in which case the sample and hold circuit 111 would not be necessary. The circuits of each of the four channels of the sample and hold circuit 111 are the same as the sample and hold circuit shown in FIG. A.

The output of channel 108, which is the mean, is then squared in a squaring circuit 112 and similarly the output of channel 110 is squared in a squaring circuit 113. Each of the squaring circuits is the same as shown in FIG. 10B. The output of the squaring circuit and the output of channel 109 are then combined in a differential amplifier 114. Similarly the outputs of the squaring circuit 113 and channel 110' are combined in differential amplifier 115. The detailed circuit of a suitable differential amplifier is shown in FIG. 11A. The formula for the computation which occurs in the differential amplifier 114 is: lX'*/N ,.(ZX/N =6,, and the formula for the mathematical computation which occurs in the differential amplifier 1 is (Z /N,,)-(E Y/ y) The outputs of the differential amplifiers are connected to the respective divide circuits 116 and 117, the details of which are shown in FIG.12. The divide circuit 116 divides the deviation 6, by the number of samples. The output of the divide circuits 116 and 117 are connected to summing amplifier (adder) 118 which performs the following mathematical computation: USE/N (6,, /N a suitable circuit being shown in FIG. 11B. The output of the summing amplifier 118 is to a square root circuit 119, the details of which are given in FIG.12 The output of the square root circuit is to the divide circuit 12 a suitable divide circuit being shown in FIG.12. The second input to the divide circuit is from a differential amplifier 121 which may be of the type shown in FIG.11A. The differential amplifier 121 provides the difference between the two means, that is, it accomplishes the mathematical computation as follows: (ZX/Nx) (Zy/Ny) The output of the divide circuit 120 is to the absolute value circuit 121, shown in FIG. 13 which provides the final result of the t test.

All of the computations necessary for the t test have been provided by the circuit of FIG. 9 and the t test result is taken at the output 123. The t test computation performed by the circuit of FIGS is as follows:

A suitable squaring circuit, as shown in FIG. 10B, uses three integrated circuits. The integrated circuits and 151 are operational amplifiers and may be of the type Motorola No. MC l556-G. That integrated circuit is a compensated and monolithic operational amplifier. The integrated circuit 152 is a multiplier which, suitably, may be Motorola Type l594-L. The multiplier, as its two inputs 153 and 154 derived from a common line 155 which is the output of the operational amplifier 150, and acts to square the input from line 155; that is, its inputs are tied together. A suitable integrated circuit is a monolithic four-quadrant multiplier wherethe output voltages are a linear product of two input voltages. The Motorola 1594-L is a variable transconductance multiplier with internal level shift circuitry and voltage regulation. The scale factor is adjustable and preferably is set to be one-tenth of input. An operational amplifier 151 is used to complete the multiplier connections from the integrated circuit 152. Its output 156 provides a square of the input at 157. This type of multiplier connection is described in further detail in the specification sheet dated Oct. 1970 DS-9l63 from Motorola of Phoenix, Arizona, of their 1594-L integrated circuit.

A suitable sample and hold circuit is shown in FIG. 10A. It uses an operational amplifier 140. Preferably operational amplifier 140 is an integrated circuit, for example, of the type Motorola No. I456G, described above.

A suitable differential amplifier circuit is shown in FIG. 11A. It uses an operational amplifier 160 having two inputs 161 and 162. Preferably the operational amplifier 160 is an integrated circuit. A suitable integrated circuit is Motorola No. MC l456G described in the specification sheet DS9l47Rl dated Apr. 1970 as being epitaxial passivated and monolithic. It has a power supply voltage of +18V do and 18V dc, a power bandwidth of 40K Hz and power consumption 4. .11 .w a

The summing amplifier of FIG.11B also uses an operational amplifier 165. The two inputs to be added are connected to one input of the amplifier 165. A suitable operational amplifier is the integrated circuit Motorola No. 1456G described above.

A suitable divider circuit is shown in FIG. 12. It uses a linear multiplier and an operational amplifier 171. Preferably the multiplier 170 and the amplifier 171 are integrated circuits. A suitable integrated circuit for the multiplier 170 is Motorola No. 1594, described above, and for the amplifier Motorola No. 14566, also described above. The inputs are 172 and 173 and the output at 174.

A suitable square root circuit is shown in FIG. 14. The square root circuit is a special case of a divider in which the two inputs to the multiplier are connected together. Consequently the input line 173 and the input line 172 are connected together to form a common input line 175.

A suitable absolute value circuit is shown in FIG. 13. It uses two operational amplifiers 176 and 177. Preferably they are integrated circuits and may be of the type Motorola No. 14560 described above. The input 178 is to the minus input of amplifier 176 and the output 179 is from amplifier 177. The purpose of the circuit of FIG. 13 is to provide a quantity regardless if the X or the Y terms are larger, the absolute value being the THE PROGRAMMED TESTING METHODS In the firet method, an alternating series of flashes (F) and clicks (C) are presented as follows: F, C, F, C, F, C, F, C, F, C, F, C, etc., until some 200 presentations of each stimulus have occurred. As the programmed stimulator presents this alternating sequence, the evoked responses are alternately directed to two different channels of the average response computer (ARC), one computing the visual evoked response (VER), the other computing the auditory evoked response (AER). The regular alternation of visual and auditory stimuli constitutes a completely predictable sensory pattern. The VER and AER resulting fromsuch predictable stimulation are recorded in any acceptable fashion: photograph, ink record, electronic memory device. Now a second sequence of 200 flashes and clicks is presented, but the different sensory stimuli are in random sequence, as for example:

F, C, F, F, C, F, C, C, C, F, C, F, CC, F, F, F, etc. As the programmed stimulator presents this random sequence, the evoked responses are appropriately switched to two different channels of the ARC, and the VER and AER are again computed. This random) sequence constitutes a completely unpredictable sensory pattern.

Visual evoked responses (VERs) and auditory evoked responses (AERs) from predictable and unpredictable stimulus sequences are then compared. The finding of marked differences between the responses elicited by predictable and unpredictable stimuli would strongly suggest that the subject perceived the alternating pattern as an orderly series of events. That perception is a cognitive process, involving short-term memory. Differences in evoked responses to predictable and unpredictable events would be expected to appear especially in the period from 100 to 300 milliseconds after the stimulus and are illustrated in FIG. 2. Study of the details of differences might provide information about the cause of the cognitive deficit.

The second method for assessing cognitive process is to establish a predictable pattern of stimulation and abruptly alter it. For example, F-F, F-F, F-F, FF, F-Q Computation of the VER at the time of the omitted flash would reveal a potential evoked by the absent but predicted event.

In the charts of FIG. 3, waveforms of different test patients are shown, the time is in milliseconds and the output in microvolts. These charts are an illustration of the second method. In the waveform A, a flash and its evoked response occurs at points 21, 22, 23, 24, 25 and 26. This shows the normal response to the flash. Waveform B shows a flash and its evoked response at 31, 32, 33, 34 and 35. At 36 there is no flash, but the subject's short-term memory has the expectation of a flash and shows the same waveform as if the flash occurred. This is the normal response In waveform C the flash and its evoked response are at points 41, 42, 43, 44 and 45. At point 46 no flash occurs and there is no response and no short-term memory. This is an abnormal response and indicates the absence of short-term memory. Such an absence may, for-example, be associated with brain damage. 4

As another example of a suitable pattern using the second method, a flash and a click soundmay constitute a pair of stimuli. The pattern, with 5 seconds of rest between eahc pair, would be as follows: click-flash- (Sseconds rest); click-flash-(S seconds rest); clickflash-(S seconds rest); click-flash-(S seconds rest); click. The brain wave would then be examined for the presence or absence of the expectancy of the omitted flash" from the last pair of stimuli.

A third method consists of presenting the same stimulus in repeated blocks of trials. For example, a 2 per second flickering light is presented for 50 seconds and the average response is computed in one channel of the ARC. After a 10-second pause, the 2 per second flicker is again presented for 50 seconds and an average response computed in the second channel of the ARC. After 10 seconds, another 100 flashes at 2 per second are averaged in the third channel. After 10 seconds, a buzzer sounds and a 5 per second flicker is presented for 20 seconds and the response averaged in the fourth shamel- The normal subject will show a progressive diminution to the repeated presentation of the same stimulus, due to habituation to a meaningless event. Thus the third average response will be smaller than the second, which will be smaller than the first. Presentation of the buzzer will cause dishabituation, and this will be further increased by the change in stimulus frequency, causing a marked increase in the size of the fourth average. in abnormal subjects, habituation wili be slower or absent and dishabituation will not occur, as seen in FIG. 4.

A fourth method consists of sensory-sensory conditioning. The response from the occipital area of the head, over the visual cortex, is utilized. A click control average response is obtained in one channel of the ARC, while 50 clicks are presented at the rate of l per second. A click plush flash control average response is then obtained in a second channel of the ARC, while 50 simultaneous click-flash paired stimuli are presented. A conditioning period then intervenes,during which 300 events occur. Each event consists of click alone, followed 250 milliseconds later byv click plus flash. The interval betweenthe click plus flash of each event and the click of the following event is one second. After the completion of the conditioning period, a test period occurs. The test period consists of 50 eventsEtch composed of click alone, followed 250 milliseconds later by click plus flash. By electronic switching, the response to click alone is averaged in a third channel of the ARC, while the response to click plus flash is averaged in the fourth channel. Comparison of channel one with channel 3 and of channel 2 with channel 4 reveals whether the conditioning procedure has altered the response of the visual cortex to the click. Changes will be observed in normal but not in abnormal subjects. The failure of abnormal subjects to show change may be due to a diffuse deficit in cognitive processes such as might occur in a mentally retarded child, or may be due to a specific deficit in associational mechanisms such as might occur in a child with an epileptic focus in the auditory cortex. By appropriate variation of the sensory modality of the first and second stimuli comprising the conditioned stimulus (FIRST) and unconditionedstimulus (SECOND) of a stimulus pair, it would be possible to discriminate between diffuse and specific deficits, accomplishing differential diagnosis. This method is illustrated in FIG. 5.

The fifth method involves the presentation of stimulus sequences which share a common pattern although varying in their specific stimulus composition, and searching for invariant features in the evoked response. For example, a large square figure is briefly shown on a screen to the subject, followed by a small square figure. The stimulator consists of a slide projector 50 which rapidly changes the slides being projected on screen 51, as shown in FIG. 6. That sequence of large square followed by small square is repeated, for example, for 30-100 times. The subjects brain wave response to these two stimuli is averaged in channels 1 (large) and 2 (small) in the average response computer which reduces the adverse effects of noise. The results are recorded on recorder 11. Subsequently a large round figure is shown, followed by a small round figure. That pattern is rapidly repeated and the brainwaves averaged and recorded as before, with large circles in channel 3 and small circles in channel 4.

The recorded brainwaves from the two patterns are then compared. If the subject perceives squares and circles as different, two different waveshapes, corresponding to the two stimuli, will be recorded. That itself is a test of visual cognition. If the subject is of normal intelligence, for example, a young non-reading child of normal intelligence, then the recorded brainwave pattern for the first set (large and small square shapes) will differ from the recorded brainwave pattern for the second set (large and small round shape). Further, the normal person recognizes the similarity of shape (squareness vs. roundness) and tends to disregard the dissimilarity of size. His brain waves correspond with that recognition. Therefore, channel 1 will resemble channel 2 and channel 3 will resemble channel 4. In contrast, a non-normal subject may perceive squares and circles as the same, or may fail to perceive large and small figures as similar, although their shape is the same (FIG. 7). The presentation of figures and the recording of the resulting brain wave is therefore a test of normal pattern perception. Such normal pattern response may be a prerequisite for reading or normal development. Its lack denotes that the subject may require special forms of training and care.

I claim:

1. Apparatus for the testing of a subject which includes a plurality of electrodes adapted to be connected to the head of the subject to monitor his brainwaves, an amplifier connected to said electrodes to amplify said brainwaves, an electroencephalograph connected to said amplifier, switching means connected to said electroencephalograph, a t test computer whose input is connected to the output of said electroencephalograph, said computer having a first squaring circuit, an average response computer having a plurality of channels and being connected to said first squaring circuit, a second squaring circuit connected to said average response computer, a first differential circuit connected to said average response computer and said second squaring circuit, a first divider circuit connected to said first differential circuit and to said average response computer, a summing circuit connected to said first dividing circuit, a square root circuit connected to said summing circuit, a second divider circuit connected to said square root circuit, a second differential circuit connected to said second divider circuit and to said average response computer, and an absolute value circuit connected to said second divider circuit, a recorder connected to said t test computer to record the averaged brainwaves, a programmed timer connected to and controlling said switching means, and stimulus means connected to said programmed timer and controlled by it.

2. The apparatus for the testing of a subject as in claim 1 wherein the programmed timer has stored therein a plurality of alternative programs and the apparatus includes a program switching mechanism whereby one of the alternative programs may be selected.

3. The apparatus of claim 1 and including means to set within the t test computer the number of sample sweeps N and the level of significance P to provide a go no go" signal to said recorder.

4. The apparatus of claim 1 and also including variable setting means to set within the t test computer the t test standard value and the maximum number of sample sweeps N, upon attainment of which standard t value a control signal is provided by said t test computer to said programmed timer.

5. An apparatus as in claim 1 wherein within the said t test computer said first squaring circuit includes two squaring means and wherein two sampling lines are connected to the output of said electroencephalograph, the said averaging circuit of said I test computer is a four-channel average response computer whose inputs are the said two sampling lines and the said two squaring means, and the inputs of which said two squaring means are connected to said sampling lines. 

1. Apparatus for the testing of a subject which includes a plurality of electrodes adapted to be connected to the head of the subject to monitor his brainwaves, an amplIfier connected to said electrodes to amplify said brainwaves, an electroencephalograph connected to said amplifier, switching means connected to said electroencephalograph, a t test computer whose input is connected to the output of said electroencephalograph, said computer having a first squaring circuit, an average response computer having a plurality of channels and being connected to said first squaring circuit, a second squaring circuit connected to said average response computer, a first differential circuit connected to said average response computer and said second squaring circuit, a first divider circuit connected to said first differential circuit and to said average response computer, a summing circuit connected to said first dividing circuit, a square root circuit connected to said summing circuit, a second divider circuit connected to said square root circuit, a second differential circuit connected to said second divider circuit and to said average response computer, and an absolute value circuit connected to said second divider circuit, a recorder connected to said ''''t'''' test computer to record the averaged brainwaves, a programmed timer connected to and controlling said switching means, and stimulus means connected to said programmed timer and controlled by it.
 2. The apparatus for the testing of a subject as in claim 1 wherein the programmed timer has stored therein a plurality of alternative programs and the apparatus includes a program switching mechanism whereby one of the alternative programs may be selected.
 3. The apparatus of claim 1 and including means to set within the t test computer the number of sample sweeps N and the level of significance P to provide a ''''go - no go'''' signal to said recorder.
 4. The apparatus of claim 1 and also including variable setting means to set within the t test computer the t test standard value and the maximum number of sample sweeps N, upon attainment of which standard t value a control signal is provided by said t test computer to said programmed timer.
 5. An apparatus as in claim 1 wherein within the said t test computer said first squaring circuit includes two squaring means and wherein two sampling lines are connected to the output of said electroencephalograph, the said averaging circuit of said t test computer is a four-channel average response computer whose inputs are the said two sampling lines and the said two squaring means, and the inputs of which said two squaring means are connected to said sampling lines. 